A major review has been written on the application of the Karplus equation to the NMR coupling constants of carbohydrates, which is one of the key methods for determining the molecular geometry of saccharides. The information gathered for the review is being used to interpret the dependence of the nitrogen-15proton coupling constants of amino sugar derivatives on atomic dihedral angle, and the stereochemical orientation of electronegative substituents. By using an HCN NMR cryoprobe, the results from the measurement of the nitrogen-15proton coupling constants of amino sugars by two different HSQMBC methods have been compared. Because of noise-producing, cross-talk between the deuterium and nitrogen-15 RF circuits of the cryoprobe in the CPMG-HSQMBC method, it appears that measurements with this probe will best be conducted by using an HSQMBC method having shaped, adiabatic nitrogen-15 RF pulses, instead of the CPMG pulse sequence. Application of the latter technique has been tested on fortamine, a diaminodideoxycyclitol component of fortimicins.